Poker equity question

In Bill Chen's book 'The Mathematics of Poker', it states that "the equity of our random hand against a distribution of AA-JJ and AK is about 24.95%". This refers to a game of no-limit holdem, 2 players left, where the pot is $45 (big blind, small blind and one $30 bet), and the player is risking $190 to jam the pot.

It starts by saying we have an equity of about 45%, which I'm fairly certain comes from equity = cost of call/new pot size (in this 190/415).

Despite my best efforts, I haven't been able to figure out where 24.95% comes from though.

Preflop allin means that you both put all of your chips to the pot preflop, so there flop, turn and river is dealt without any actions and the one with the better hand after river wins the pot. Your equity (24,95%) means that it is your chance to win the pot, thus your equity shares. Of course you can't win 24,95% of the pot, you either win it or lose it (or in rare occasions you have a tie). But if the same situation happens countless of times, that would be your average chance to win.

Think about flipping a coin, you have 50% chance to win it. If we flip it, it can't be a tie. Either one of us win it, but on average you will win 50% of flips.